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PostPosted: Wed Jan 22, 2020 8:34 am 
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Just a quick one ...

When you pull the handbrake, both rear shoes move but is it only the back facing shoe that grabs and holds??

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PostPosted: Wed Jan 22, 2020 9:31 am 
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1275cc
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I thought that both shoes are pushed apart into the drum by the hand brake lever - the 2 piece T bar riveted together.
The cable pulls the short part of the lever directly onto the rear facing shoe but as it does, it causes the longer part of the lever to push the front shoe into the drum too, because the lever is now longer than it was at rest. To get one shoe to grab and hold, the lever has to push against the other front shoe, so they both should contact the drum evenly.

The rear facing shoe will usually show more wear than the other because it is the "leading" shoe when you use the hydraulic brakes.


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PostPosted: Wed Jan 22, 2020 11:17 pm 
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848cc
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Thanks Bill. Out of pure curiosity I played with the movement of the lever arms on photoshop and you are right.

I see it as a two stage action. And like you’ve said, the rear pad’s leading edge bites into the drum first. As you pull more on the handbrake, the whole lever pushes off the rear pad and forces the trailing edge of the front pad to bite.

Here’s my dodgy little sketch.

Are we on the same page?

Image


Sent from my iPhone using Tapatalk

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Australian 69 DeLuxe w/ hydro suspension. Single HS4 (twin HS2 being assembled). 1275 1100s engine (998 due for rebuild) . Clubman remote gear change. Automatic front subframe.


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PostPosted: Thu Jan 23, 2020 8:59 am 
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1275cc
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Good illustration. I was trying to think of a visual to explain it. That was what I meant.
That whole lever (the one inside the brake drum, not the one the driver uses) "floats", so has to push off one of the shoes to wedge against the other shoe.


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PostPosted: Thu Jan 23, 2020 10:40 am 
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Yeah... I couldn't understand why the whole lever "floats" but it makes sense now. I've been trying to figure it out for ages!!!

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PostPosted: Thu Jan 23, 2020 2:03 pm 
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This is how the manufacturer Lockheed explains the operation of the rear brakes.

The complete publication is posted here - http://www.ausmini.com/forums/viewtopic ... 25&t=98788

Click on the image to enlarge it.

Attachment:
Lockheed Brake Clutch Service Manual Mini Front Cover.jpg


Attachment:
Lockheed Brake Clutch Service Manual Mini p16.jpg


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PostPosted: Thu Jan 23, 2020 3:15 pm 
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That's a cracker manual!!! It looks like I've got the concept correct except the long arm moves first and then the short one. I was so confused by this floating lever... thanks.

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PostPosted: Thu Jan 23, 2020 4:39 pm 
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3ug3 wrote:
That's a cracker manual!!! It looks like I've got the concept correct except the long arm moves first and then the short one. I was so confused by this floating lever... thanks.


I think you have worked it out.
But in reality, the movement back and forward has to happen at about the same time to have any impact on the brake drum.


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PostPosted: Fri Jan 24, 2020 1:29 pm 
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848cc
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Once the rear shoe contacts the drum it cannot move any further laterally so the movement is then transferred to the front shoe via the arm. This is why it’s quite important to keep them adjusted. The further the rear shoe has to travel to contact the drum, the further the handbrake needs to be pulled to move the front shoe against the drum. The problem becomes even worse if one side is further out of adjustment than the other as they don’t use a balance bar. So once one drum has locked the other cannot be pulled any tighter (not taking into account cable stretch)


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PostPosted: Fri Jan 24, 2020 10:16 pm 
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Isn’t the balance bar the short lever that the two handbrake cables attach to and then this is pulled by the handbrake lever ?

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PostPosted: Sat Jan 25, 2020 4:28 am 
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All Oz made Minis have 2 separate cables onto the handbrake lever.

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